This invention relates to a hydraulic servovalve assembly optically operated and more particularly to a feedback loop system used with a fiber optic transmission line for operating a jet pipe connected to a hydraulic servovalve.
In a patent application entitled AIRCRAFT FIBER OPTIC CONTROL DEVICE, filed Mar. 16, 1984, Ser. No. 590,151 by the subject inventor, an electrically passive open hydraulic servovalve system is described. The system is used to minimize the effect of electromagnetic pulses and electromagnetic interferences on aircraft control systems. This type of basic optical hydraulic servovalve system can be greatly improved by incorporating an electrically passive optical feedback loop internal to the servovalve assembly. Operating parameters such as servovalve gains and phase shift are greatly improved when feedback concepts can be integrated into the servovalve system.
In a basic optical hydraulic servovalve operation, a series of energy conversions consisting of converting light energy into heat energy then into mechanical function and finally into change in hydraulic flow rate is provided. Functionally, this process is an integration operation with the inherent undesired phase shift that is characterized by integration processes. If the optical hydraulic servovalve input signal is the "error signal" derived by comparing the optical hydraulic servovalve hydraulic output with the optical input instead of an open loop input signal, this feedback loop will minimize the inherent phase shift due to the integration process and enhance the servovalve gain.
During the test and operation of the optical hydraulic servovalve a large loop feedback approach was used to demonstrate the valve of a feedback system in reducing the servovalve phase shift and thereby enhancing servovalve gain. This feedback loop was complicated and encompassed numerous disciplines such as hydraulic pressure sensing, optical signal transmissions and electronic processing. The performance of large feedback schemes are limited since the error signal contains nonlinearities of many subsystems which often produce instability and runaway servosystems.
In the following United States patents; U.S. Pat. No. 27,352 to Stern, U.S. Pat. No. 2,726,617 to Zand, U.S. Pat. No. 2,996,072 to Atchley, U.S. Pat. No. 3,401,603 to Coakley et al, U.S. Pat. No. 3,424,183 to Coakley, U.S. Pat. No. 3,433,133 to Brewer et al and U.S. Pat. No.3,908,471 to O'Connor et al various types of servovalve control systems using jet pipe assemblies and expandable bellows are described. None of these prior art patents describe the unique features and advantages of the subject invention.